Alditol acetal composition and its use in plastic and gelled materials

ABSTRACT

The present invention relates to improved alditol acetal compositions, in particular 1,3-2,4-di(benzylidene) sorbitol (DBS) or one of its alkylated derivatives. 
     The improvement in these compositions is expressed in particular in terms of flow behavior and/or thermal stability. It is obtained by combining the alditol acetal with an additive selected from tocopherols, polyols and certain of their respective derivatives. 
     These additives may act as binding or densifying agents and/or stabilizing agents or odor maskers. 
     The alditol acetal and additive are advantageously combined by cold mixing, followed by granulation or compaction, also cold. 
     The compositions of the invention, for example based on DBS or the methylated derivatives of DBS, are in the form of densified or compacted powders, granules, pellets, pastilles or extrudates. 
     They are used in particular for preparing plastic or jellified materials or additives for these types of materials.

FIELD OF THE INVENTION

The present invention relates to an improved composition of alditolacetal, in particular dibenzylidene sorbitol or one of its derivatives.

It relates in particular to a new powdery composition of an alkylatedalditol diacetal.

It is also intended to provide a new process for improving the flowbehavior and/or stability of alditol acetal compositions.

Finally the present invention also relates to use of said compositionsfor preparing plastics materials or jellified materials or additivesintended for use in said materials.

BACKGROUND OF THE INVENTION

It is well known that alditol acetals such as dibenzylidene sorbitol andits derivatives may be used as additives, in particular as nucleatingagents or clarifying agents for plastics materials such as polyolefins.

These products are also used as agents for jellifying or modifying theviscosity of a variety of materials such as compositions for cosmetic orpharmaceutical use, adhesive compositions or paints. These compositionsmay also be shaped within other articles such as rods or sticks of glueor cosmetic materials, for example deodorants or air fresheners.

One of the main disadvantages associated with the industrial use ofalditol acetals such as dibenzylidene sorbitol and its derivativesrelates to the poor flow behavior of these products. This is due, atleast in part, to the generally very powdery and very tacky character ofthese products. This produces problems during industrial operations suchas transporting, crushing, bagging, metering, mixing, storing,cleansing, etc.

In particular, alditol acetal powders readily form “domes” in storagetanks and/or transport piping. This prevents or impedes the routing,metering, and/or evacuation of these products when using feeding hoppersand metering systems in industrial units, for example units intended forthe preparation of plastics materials or additives for plasticsmaterials.

“Plastics materials” are understood to mean in particular polyolefins,especially all polymers based on propylene and/or ethylene, polyamides,thermoplastic polyesters, vinyl resins, acrylic resins and mixtures ofthese.

This flow behavior problem of powdery forms of alditol acetals has notyet been resolved in a practical industrial manner, other than bymanufacturers and/or users of these products using modified devices suchas special pneumatic feeding systems or PTFE-lined hoppers.

In addition to the fact that these types of devIces may be costly and/orcomplex, they do not always prevent, the “dome” phenomena mentionedabove or at the very least fouling problems which appear in hoppers,metering systems or, further downstream, screw conveyors supplyingmixtures to preparation units for plastics or jellified materials.

Moreover, even within compositions of materials into which they can beintroduced and metered in a satisfactory manner, alditol acetals mayexhibit a poor dispersing capacity. This phenomenon can produce, inparticular in plastics and jellified materials, a heterogeneity or somedegree of degradation of the final characteristics of said materials(general appearance or organoleptic, optical, mechanicalcharacteristics, etc).

A variety of technologies has been proposed in order to alleviate theproblems mentioned above of Door dispersibility of alditol acetals, inparticular of dibenzylidene sorbitol and its derivatives. For example,Japanese patent JP 60-101131 describes drying then finely crushing analditol diacetal previously treated with terephthalic acid in thepresence of an anionic surfactant.

Lyophilisation of a gel of alditol diacetal in a solvent has also beenrecommended, as disclosed in Japanese patent JP 62-253646. Thelyophilized product thus obtained has a low “after tamping down”density, that is the density is in the order of 100 g/l, and is alwayssignificantly less (by a factor of about 3) than that of the initialalditol diacetal.

More recently, patent EP 569 198 has disclosed ultrafine crushing ofalditol diacetals on modified devices, for example combining a fluidizedbed and a high speed turbine, in order to obtain products with anaverage particle size which is especially small, that is at most 15 μmand preferably less than 6 μm.

On reading example 2 of the above document it seems that this type ofultrafine crushing applied to dibenzylidene sorbitol with the brand name“MILLAD® 3905” is accompanied by a very significant reduction (by afactor of about 3.3) of the “after tamping down” density (“packed bulkdensity”) of the product.

Still more recently, other technologies have been recommended with theobjective of improving the dispersibility of alditol diacetals, inparticular:

the preparation, by drying/spraying, of a fine powder based on a mixtureof an alditol diacetal and a special phosphite, said mixture having beenpreviously solubilized in a solvent (patent EP 651 006), or

forced drying and crushing, in particular in an instantaneous dryer, ofdamp alditol diacetal, the dried/crushed product obtained having a verylow residual water content (0.01%) and an apparent density in the orderof about 200 g/l (patent JP 06-048783).

The result is that the methods recommended for guaranteeing gooddispersibility of alditol acetals within plastics materials etc, aregenerally complex and/or costly or even dangerous, in particular due tothe fact that they involve the use of specific drying equipment,crushing equipment and/or solvents.

In addition, as indicated above, these methods generally have theobjective of or the effect of significantly reducing the density ofalditol acetals, which increases their dusty character and dangerousness(risks of explosion and inhalation) and worsens their ability to flowfreely.

Another disadvantage associated with the industrial use of alditolacetals, or at least in some of them such as, for example, certainalkylated or halogenated derivatives of dibenzylidene sorbitol,originates in the unstable character of these products. This instabilityis exhibited in particular by odiferous problems and by a reduction ineffectiveness under some conditions of use.

These problems may be detected organoleptically in the initial product,i.e. even before any processing or special use of the product.

They may be detected organoleptically only when the alditol acetal isactually used in an industrial process, for example during thermoformingof a plastics material in which alditol acetal has been incorporated.

This type of thermal treatment may, inter alia, generate, encourage oramplify decomposition phenomena, in particular hydrolysis and/orsublimation of the alditol acetal and the emission of undesirable odors,in particular of an aldehyde type.

This is particularly undesirable in the case of materials intended to beused in contact with foodstuffs, pharmaceuticals or cosmetics.

This instability, in particular thermal instability, of alditol acetalsis generally accompanied by a reduction in their effectiveness asnucleating or clarifying agents, the decomposition or hydrolysisproducts of alditol acetals not being able to act in this way.

A variety of processes has been suggested for improving the stability,in particular thermal stability, of alditol acetals, in particulardibenzylidene sorbitol and its alkylated or halogenated derivatives, andthus for minimizing or masking, or even suppressing odiferous problemsand/or problems of lowering in the effectiveness associated with the useof these products.

These problems may be due in particular to the residual presence, evenwithin the plastics materials, of species which are capable ofcatalyzing the decomposition of alditol diacetals, such as residualamounts of polymerization catalysts with an acid nature, as described inpatent EP 68 773.

The above patent recommends the incorporation, within particularplastics materials (low density linear polyethylenes with a highconcentration of residual catalysts), of inhibitors of the decompositionof diacetals selected from a wide variety of chemical families (metalsequestering agents, amines, alkenes, epoxides, cyclic esters, etc).

It has also been proposed, as in patent EP 298 375, to treat the surfaceof alditol diacetals with metal salts of aliphatic acids or lactic acidswith the objective of improving the thermal stability. In the examplesin the above patent, 1,3-2,4-di(methylbenzylidene) sorbitol can bestabilized by hot mixing with an equivalent weight of calcium stearate,the mixture obtained being crushed after cooling before being introducedinto a polypropylene resin.

Patent EP 361 087 describes the incorporation, into a crystallinepolyolefin, of cyclodextrine as a stabilizing agent for dibenzylidenesorbitol or its derivatives.

It has also been recommended that a primary aliphatic amine beincorporated into polypropylene with the objective of reducing the odorgenerated by the alditol diacetal which it contains, as described inpatent JP 4-82890.

Patent EP 522 558 describes the stabilization of dibenzylidene sorbitoland its derivatives by mixing, preferably in a solvent medium(methanol), with 0.05 wt. % to 20 wt. % of sorbic acid and/or potassiumsorbate.

Patent JP 9-286788 describes the stabilization of DBS and derivatives byadding polyalcohols, this addition taking place either during thepreparative process for alditol diacetal or later by a physical mixingprocess, in the dry or in the presence of a solvent such as water or analcohol.

According to the above patent, in particular the examples, the polyol isadvantageously introduced in relatively high concentrations, inparticular at a concentration of 20% to 150% with respect to the weightof the diacetal.

Moreover, the examples always provide for the use of the polyol in asolvent, in this case isopropanol, in which the diacetal is dispersed,the latter generally being added in the form of a suspension in anothersolvent, in this case methanol.

The composition of this diacetal is recovered after heating andhomogenizing the resulting mixture with the evaporation of any solventused.

It seems, however, as will be examplified below, that a compositionprepared in this way still has a poor flow behavior and a tackycharacter. In addition its aerated density is not increased in any case.

Finally, patent EP 569 198 mentioned above, relating to the sorbitol orxylitol diacetals with ultrafine particle sizes, indicates that thesetypes of products reduce the color and odor problems in the finalproducts. This patent is the only one which actually describes thepossibility of obtaining, by applying a single process (ultrafinecrushing), products which are a priori improved both in terms of“dispersibility” and in terms of “odor”.

However, as indicated above, this process involves the use of veryspecific crushing devices and leads to the production of powdery formswhich have a very low density and flow with great difficulty.

OBJECTS AND SUMMARY OF THE INVENTION

Thus there is a need to provide a simple, non-costly and non-dangerousmethod allowing an improvement in the flow behavior and/or the stabilityof alditol acetals and which, obviously, does not damage otherfunctional characteristics of these products and does not reduce therange of application, in particular as additives for plastics materialsand jellified materials.

The Applicant has found, after a number of research projects, that sucha method can comprise adding to said acetals , with certain selectedcompounds, that s tocopherols and their derivatives, polyols and theirnon-fatty derivatives and mixtures of these.

To be more specific, the present invention provides a composition ofalditol acetal with improved flow behavior and/or improved stability,characterized in that it includes at least one alditol acetal and atleast one additive selected from the group comprising tocopherols andtheir derivatives, and also polyols and their non-fatty derivatives, andthat it has an aerated density greater than 250 g/l.

The alditol acetal composition in accordance with the invention can alsobe characterized in that the alditol acetal and selected additive suchas defined above have been subjected in the presence of each other to ashaping and/or densification procedure, in particular granulation,compaction or extrusion.

The improvement in flow behavior of compositions of alditol acetalswhich can be obtained by using such additives may be recognized inparticular by:

a less marked propensity to create domes, or to cause fouling and/orother hindrance, within classical industrial devices for storing,transporting, evacuating, metering or mixing and/or

a less marked propensity to generate “fines” or dusts during handling oruse.

To this end, the additives mentioned above may act as binding agents ordensification agents for alditol acetals.

The improvement in the stability of alditol acetal compositions whichmay be obtained by using said additives can be recognized in particularby a less marked propensity, during and/or after thermal processing, toemit undesirable odors which can be detected organoleptically and/or byan even more improved transparency of the plastics materials in whichsaid compositions are incorporated.

To this end, the additives mentioned above may also act, with regard toalditol acetals, as stabilizing agents or odor masking agents.

“Alditol acetal” in the context of the present invention is understoodto mean in particular alditol diacetals, in particular those resultingfrom the dehydrocondensation in two positions of an alditol with 5 or 6carbon atoms and a benzoic aldehyde.

Said alditol may be selected in particular from the group consisting ofsorbitol, xylitol, mannitol, ribitol, arabitol and iditol. It may bemodified at the level of the last carbon atom in the chain, inparticular by introducing a carboxylic group and thus consists of agluconate or a xylonate.

The benzoic aldehyde used with the objective of preparing alditolacetals which can be used in accordance with the invention may consistin particular of benzaldehyde, 1-naphthaldehyde or of any one of theirrespective derivatives.

In a preferential manner, the benzoic aldehyde used consists ofbenzaldehyde or one of its derivatives, for example those derivativessubstituted in one or several positions by an alkyl, alkoxyl, hydroxyl,halcen, thioalkyl or sulphoalkyl group.

When the benzaldehyde is substituted in several positions, thesubstituents may or may not be identical. The substituents may also belinked to form a carbon ring.

In an advantageous manner, the benzaldehyde is substituted in one, twoor three positions by an alkyl group, in particular methyl or ethyl, bya halogen group, in particular a chlorinated or fluorinated group, by ahydroxyl group and/or an alkoxyl group, in particular methoxyl. Thesubstitution may be made in particular in positions 2 (ortho), 3 (meta)and/or 4 (para) of benzaldehyde.

The alditol acetal which can be used in accordance with the inventionmay be selected in particular from those described in European patentsEP 286 522 and EP 421 634 and/or in any of the patents described abovewithin the context of the present description.

The alditol acetal is preferably an alditol diacetal selected from thegroup comprising 1,3-2,4-di(benzylidene) sorbitol (called DBS below),1,3-2,4-di(benzylidene) xylitol (called DBX below), and theirderivatives, in particular alkylated and/or halogenated derivatives,preferably chosen among DBS and its alkylated derivatives.

In a particularly advantageous manner, the alditol diacetal is chosenfrom among methylated derivatives of DBS, in particular those obtainedby dehydrocondensation of sorbitol and a methylated benzaldehyde, withthe methyl groups in at least positions 3 or 4 of the ring (meta or parapositions respectively).

The methylated derivatives of DBS comprise in particular the followingproducts:

1,3-2,4-di(4-ethylbenzylidene) sorbitol,

1,3-2,4-di(4-methylbenzylidene) sorbitol,

1,3-2,4-di(3-methylbenzylidene) sorbitol, and

1,3-2,4-di(3,4-dimethylbenzylidene) sorbitol.

The additives which can be used in accordance with the invention withthe object of improving the flow behavior and/or stability of alditolacetals are, as specified above, selected from among tocopherols andtheir derivatives, and polyols and their non-fatty derivatives.

“Tocopherols” in the context of the present invention are understood tomean in particular “tocol” or3,4-dihydro-2-methyl-2(4,8,12-trimethyltridecyl)-2H-1-benzopropane-6-oland all its derivatives, in particular alkylated derivatives, which maybe of natural or synthetic origin.

Alkylated derivatives of tocol may comprise in particular methylatedproducts which are methylated in at least one of positions 5, 7 and/or8, of the benzopyrane ring in tocol and in particular correspond to α,β, γ and δ tocopherols and mixtures thereof.

In an advantageous manner a natural or synthetic tocopherol made upentirely or in part of α-tocopherol and, in particular, constituted ofnatural or synthetic vitamin E, is used.

The derivatives of tocopherols may comprise esterified tocopherols, inparticular those esterified in position 6 of the benzopyrane ring, whichare esterifed by a variety of substituents such as acetate or succinategroups.

“Derivatives of tocopherols” in the context of the present invention arealso understood to mean tocotrienol and all its alkylated and/oresterified derivatives. They may be alkylated derivatives such as α, β,γ and δ tocotrienols and mixtures thereof.

The compounds and derivatives previously mentioned are largely describedin the literature, for example in:

“The Merck Index”, 10th edition, 1983, pp. 1358-1360 and 1437,

“Vitamin E: Biological and Clinical Aspects of Topical Treatment” by K.Furuse, Cosmetics & Toiletries, Vol. 102, Nov. 1987, pp. 99-115,

European patent EP 384 472, p.3 lines 45 to 47,

these passages being incorporated into the present description.

Polyols which may be used as additives in accordance with the inventionare in particular chosen from among the sugar alcohols, glycerol,pentaerythritol and their respective non-fatty derivatives.

“Sugar alcohols” are understood to mean the previously mentionedalditols for preparing alditol acetals, maltitol, isomaltitol,hydrogenated isomaltulose, maltotriitol, hydrolysates of hydrogenatedstarch, erythritol, lactitol and mixtures thereof.

The non-fatty derivatives of all these products may be produced fromthem by varying degrees of dehydration, condensation, polymerization,physical modification and/or chemical modification. They may consist forexample of isosorbide, isomannide, sorbitan, gluconates, xylonates,dipentaerythritol, phenolic derivatives of pentaerythritol, non-fattyderivatives of glycerol such as ethoxylated derivatives, etc.

In a preferential manner, the polyols which can be used in accordancewith the present invention are chosen from among sorbitol, glycerol andpentaerythritol.

According to a first variant, the alditol acetal composition withimproved flow behavior and/or improved stability in accordance with theinvention is characterized in that it comprises:

50 wt. % to 99 wt. % of alditol acetal(s), and

1 wt. % to 50 wt. % of at least one additive as defined above, thesepercentages being expressed with reference to the total weight ofalditol acetal(s) and additive(s) contained in said composition.

Said composition of alditol acetal advantageously comprises 1 wt. % to20 wt. %, preferably 3 wt. % to 20 wt. %, of at least one such additive.

The composition of alditol acetal in accordance with the invention mayhave a number of different solid forms, preferably a powdery and/orgranular form and in particular the form of a densified or compactedpowder, granules, pellets, pastilles or extrudates.

The powdery forms such as densified or compacted powders may have inparticular the form of free-flowing compositions (free-flowing powders)based on particles with variable shape and dimensions and, for example,agglomerates in the form of flakes in which the largest dimension isgenerally in the range of about 1 mm to about 10 mm and the thickness isless than about 1 mm.

These various solid forms may besides contain other components than thealditol acetal and the additive. When compositions according to theinvention are intended for the preparation of plastics materials, theymay, for example, contain one or more other constituents chosen fromamong the additives described in the previously mentioned patents suchas, inter alia, antioxidant agents, stabilizers, neutralizers, chelatingagents, nucleating agents, clarifying agents, lubricants, anti-UV,antihaze agents, antiblocking agents, antistatic agents, fillers,pigments, phosphites.

The bringing into contact of the alditol acetal and the additive withinthe composition according to the invention may take place in a varietyof manners and in particular by hot or cold mixing, generally followedby one or other of the known methods of granulating, compacting,pelletising or extruding.

The Applicant first found out that the bringing into contact of thealditol acetal and the additive could not merely result, to beefficient, from a simple physical mixing of the two constituents.

The Applicant then discovered, as will be illustrated, that it wasadvantageous to mix, cold, an alditol acetal such as a methylatedderivative of DBS and an additive such as glycerol, sorbitol orpentaerythritol, then to subject the mixture obtained, also cold, to acompacting operation, for example using a roller compactor.

By mixing or compacting “cold”, it is to be understood that theoperations are performed in the absence of any external source of heatthe use of which being intended to increase significantly, directly orindirectly, the temperature of the mixture. Also excluded is anyoperation which is intended to melt, or solubilize in a solvent, anadditive which is in a solid form at ambient temperature.

“Ambient temperature” is generally understood to mean a temperaturelower than 30° C., and generally in the range of about 15° C. to about25° C.

In the context of the invention, the additive is preferably used in thephysical state in which it is found at ambient temperature.

This method of operating at ambient temperature minimizes the risks ofdegradation of the alditol acetal, the energy requirement and thehazards associated with a process which would involve operations such asheating and/or the use of a solvent.

In a particularly advantageous manner, the mixture prepared andcompacted “cold” contains an additive which has been used in a solidform, i.e. in a form which is neither liquid nor pasty, and which iskept in this form during the mixing/compacting operations.

In a surprising and unexpected manner, the Applicant found that a solidadditive (i.e. not melted nor solubilized in a solvent), amorphous orcrystalline, could act, simply by applying pressure, as a binder, andenable the production of alditol acetal compositions which aresimultaneously improved with respect to flow behavior, density anddispersibility.

According to the Applicant, the non-molten state of the binder seems toavoid the problems of adherence of the obtained composition to the wallsof the containers used for preparing, transporting, crushing, bagging,metering, mixing, storing, etc.

The Applicant has also noticed that by proceeding “cold”, in particularat ambient temperature, and by using a solid additive, the crystallinestructure of the diacetal contained within the composition is notsignificantly modified when compared with the crystalline structure ofthe original diacetal, without an additive.

Conversely, it has noticed that when using a binder in the liquid,solubilized or molten state, this crystalline structure is altered to agreater or lesser extent.

For example, FIG. I represents a scanning electron microscope photograph(SEM—magnification 3 500) of an alditol acetal composition in accordancewith the invention, obtained by compacting, on a 3-roll compactor atabout 20° C., 1,3-2,4-di(3-methylbenzylidene) sorbitol (called MDBSbelow) and 10 wt. % of a polyol which is solid at this temperature, inthis case sorbltol.

It can be seen that the crystalline structure of the diacetal containedin the composition prepared in this way is not significantly alteredsince, like the original MDBS and, more generally, like methylatedderivatives of DBS, this structure is largely present (i.e. more than50% of its weight) in the form of rods with a length in the range 5 μmto 10 μm and the contours of which are clearly defined. These crystals,like those of the original MDBS, are not oriented in a preferentialdirection.

FIG. II represents an SEM photograph of an alditol acetal compositionalso in accordance with the invention, obtained under the sameconditions but starting from MDBS and 20 wt. % of a polyol which isliquid at 20° C., in this case glycerol.

In this case the crystalline structure of the MDBS is slightly alteredand is in the form of irregular clusters, not preferentially oriented,of rods with contours which are not clearly defined and the majority ofwhich having a length less than 5 μm.

FIG. III is an SEM photograph of an MDBS composition obtained in thesame manner but in which only 10 wt. % of an additive, in this caseglycerol monostearate, was added in a molten form and kept in this stateduring the mixing and shaping operations.

In this case the crystalline structure of the MDBS is greatly altered. Acrystalline magma is present, which is more or less continuous, orientedin accordance with a preferential direction and consists of elongatedstructures which are apparently flexible and with non-defined contours.

Consequently, the present invention also provides a process forimproving the flow behavior and/or stability of an alditol acetalcharacterized in that it includes at least one step during the course ofwhich said aldatol acetal is mixed cold, shaped and/or densified, alsocold, and in particular by granulating, compacting or extruding, with atleast 1 wt. %, preferably 3 wt. % to 20 wt. %, with respect to the totalweight of the mixture, of an additive added and maintained in the solidstate, said additive preferably being a stabilizing agent or an odormasker for the alditol acetal.

The present invention also provides, as a new industrial product, analkylated, preferably methylated, alditol diacetal composition,characterized in that it:

a) flows freely,

b) contains at least one additive which:

is solid at ambient temperature,

preferably represents 3 wt. % to 20 wt. % of the total alditol diacetaland additive contained in said composition, and

c) contains an alkylated alditol diacetal most of which is in the formof rod-like crystals with a length in the range 5 μm to 10 μm and thecontours of which are clearly defined.

The compacting operations, but also the granulating or the pelletisingoperations in particular, enable the production of alditol diacetalcompositions in accordance with the invention with aerated densitiesgreater than 250 g/l, and possibly reaching 700 g/l, in a simple,reproducible and cheap manner.

“Aerated density” is understood to mean the mass per unit volume of acomposition which is measured without any tamping down or tapping. Thisfeature is measured by allowing the composition to flow under its ownweight into a 100 ml graduated cylinder through a funnel with non-rigidwalls (a paper funnel).

Despite densities of this magnitude, the Applicant observed that thesecompositions of alditol diacetals disperse in a totally satisfactorymanner within the materials in which they are introduced and then have,in a surprising manner, an undiminished effectiveness, even an improvedeffectiveness.

The improved alditol diacetal composition according to the invention isthus also characterized by the fact that it has an aerated density inthe range 275 g/l to 700 g/l, preferably in the range 300 g/l to 650g/l. This density may be in particular in the range 300 g/l to 490 g/l.

To the Applicant's knowledge, a powdery composition of an alkylatedalditol diacetal which flows freely and has this type of aerateddensity, represents a new industrial product, examples of the unexpectedadvantages of which will be given below.

Furthermore, the present invention also provides a powdery compositionof an alkylated, in particular methylated, alditol diacetal which flowsfreely and has an aerated density greater than 250 g/l, preferably inthe range 275 g/l to 700 g/l and in particular in the range 300 g/l to650 g/l.

In a very advantageous manner, such powdery compositions have an aerateddensity in the range 300 to 490 g/l.

Alditol diacetal compositions in accordance with the invention may beused in particular in the preparation of plastics materials or jellifiedmaterials, but also in the preparation of additives intended for use insuch materials.

They may be used in particular, either in the form of powders, forexample densified or compacted powders, or in the form of granulates,for the preparation of additives for plastics materials beingadvantageously in a granular form.

These types of additives may consist in particular of ready-to-usemixtures which are in the form of free-flowing granulates containing inthe final state, in addition to the alditol acetal and additive inaccordance with the invention, one or more other constituents chosenfrom the additives described in the patents mentioned above. These typesof mixtures are known to the profession by expressions such as “onepack”, “custom blend”, “pcre-blend” or “no dust blend” mixtures.

“Additives for plastics materials” are understood to mean master mixes(master batches), which have the form of granulates of plasticsmaterial, for example polypropylene, in which the additives have beenpredispersed, entirely or partly, before being eventually incorporatedinto the final product.

For whatever use the compositions in accordance with the invention areintended, in the future there will be available new methods forimproving the flow behavior and/or the stability of an alditol acetal. Aprocess may be characterized in particular in that it includes at leastone step during the course of which said alditol acetal is mixed andshaped and/or densified in any manner whatsoever, in particular bygranulating or compacting, with at least 1 wt. % with respect to thetotal weight of mixture, of an additive selected from among tocopherolsand their derivatives, polyols and their non-fatty derivatives and anymixtures of these products.

Moreover it follows that the basic concept in the present invention alsodepends on a process for densifying and/or improving the flow behaviorof a composition of preferably alkylated, even more preferablymethylated, alditol diacetal, using a stabilizing or odor masking agentfor said diacetal, said agent preferably being in the solid state duringits use.

MORE DETAILED DESCRIPTION

The invention may be understood better with the aid of the exampleswhich follow and which are given in a purely illustrative manner.

EXAMPLE 1 Preparation of Alditol Acetal Compositions According to theInvention

A commercially available alkylated derivative of DBS, in this case1,3-2,4-di(4-methylbenzylidene) sorbitol (called MDBS below) in the formof a powder which flows with great difficulty and with a low aerateddensity (160 g/l), and 11 wt. %, with respect to the weight of alditoldiacetal, of one of the following additives in accordance with theinvention: glycerol, sorbitol, pentaerythritol and vitamin E, areintroduced at ambient temperature into a mixer of the “Robot-Coupe”type.

After mixing for 5 minutes at ambient temperature, each of thecompositions thus obtained is subjected to a cold compacting operationin a triple roller compactor of the type used for refining sugar orchocolate.

The resulting compositions have a flow behavior which is very greatlyimproved and an aerated density which is very significantly increased,that is to say in the order of about 330-340 g/l (obtained with sorbitolor pentaerythritol) to about 370 g/l (obtained with glycerol or vitaminE).

This example demonstrates the importance of the additives selected inthe context of the invention as binders or densification agents foralditol acetals.

In a remarkable manner, these additives, even when introduced atrelatively low concentrations, enable the preparation of alditol acetalpowders which have simultaneously free-flowing behavior and a highaerated density.

They enable in particular the preparation of powders of alkylatedderivatives of DBS which flow freely and have aerated densities (verymuch) greater than 250 g/l. To the knowledge of the Applicant, such aresult has never been obtained previously.

EXAMPLE 2 Preparation of Plastics Materials by Using Compositions inAccordance With and not in Accordance With the Invention

A master batch based on polypropylene (grade P243L from Borealis) andwith 1.1 wt. %, with respect to the polypropylene, respectively of:

either a commercially powder of MDBS with a low aerated density such asthat described in example 1,

or each of the powders with improved flow behavior in accordance withthe invention such as described in example 1,

or powders which do not conform to the invention obtained under the sameconditions as those described in example 1, by using 11 wt. % (withrespect to MDBS) of fatty compounds such as vegetaline, triacetine,stearic acid, lauric acid, Span® 85 or Tween® 80,

is first produced in a device of the “Rheocord 90” type fitted with a“Rheomex TW 100” twin-screw extruder operating at a speed of 30 rpm andat a set point temperature of 255° C.

Each of these master blends obtained is introduced into virginpolypropylene at a concentration of incorporation such that the finalmixture, which is subjected to a second extrusion cycle, contains 0.2wt. % of MDBS, with or without an additive.

Each of the plastics materials thus obtained is injection molded at 240°C. in a press of the “All Rounder 200” type, the cooling temperature ofthe mould being fixed at 17° C.

The injection molded articles obtained were in the form of standardizedcylinders of 2 mm thickness.

EXAMPLE 3 Characterizing the Plastics Materials Obtained

For each of the injection molded articles obtained in accordance withexample 2, the gain (+) or conversely the loss (−) of transparency,calculated by the difference in the turbidity values (haze) measuredusing a sample and a control, i.e. in which 0.2% of MDBS alone has beenincorporated, was evaluated from values obtained on a “Haze Guard Plus”device.

Sensorial analysis was also used in order to detect the positive,negative or zero effect of the MDBS compositions on the odor of theinjection molded plastics material, the control again being a sampleinto which 0.2% of MDBS without an additive has been incorporated.

This organoleptic test was performed in the following manner. For eachtested composition of MDBS, 15 injection molded cylinders were takenwhich were divided between three air-tight “twist off” glass flasks witha volume of 400 ml, on the basis of 5 cylinders per flask. The cylinderswere left for 1 week in the pots at ambient temperature. They were thenevaluated “blind” by an expert panel of 15 persons.

Analysis of the evaluations obtained for each tested MDBS compositionenabled it to be compared with the control with MDBS which did notcontain an additive, in accordance with the following notation:

0: odor equivalent to the control

+: odor less perceptible than that of the control, the number of plusesbeing proportional to the reduction in the odor problem as compared withthe control

−: odor more perceptible or more disagreeable than that of the control,the number of minuses being proportional to the increase in the odorcompared with the control.

The results of these tests for transparency and odor are summarizedbelow depending on the product used in association with the MDBS.

It is understood that the improvement in the stability of the MDBS maybe represented concretely either by the improvement in one only of thetwo characteristics studied (transparency or odor), this improvementbeing accompanied at the worst by only a small negative effect on theother characteristic (odor or transparency respectively) or, preferably,by an improvement in both characteristics.

Positive (+), negative (−) or nil Gain (+)/Loss (−) of effect %turbidity (0) on odor/ (haze)/control (control) control = MDBS alone 0 0MDBS + glycerol* +18 ++ MDBS + Sorbitol* +11 0 MDBS + +9 ++pentaerythritol* MDBS + vitamin E* +4 + MDBS + vegetaline 0 −−−− MDBS +triacetine −15 −− MDBS + stearic acid −15 −− MDBS + lauric acid −24 −−MDBS + Span ® 85 +19 −−− MDBS + Tween ® 80 +10 −− *additive used inaccordance with the invention.

These results demonstrate that, from among all the products tested, onlyadditives selected in accordance with the invention enable the stabilityof alditol acetals such as MDBS to be increased, in particular byreducing or masking the detectable undesirable odors they generate, inparticular following thermal processing. It is remarkable to note thatnot only are these types of additives capable of improving both the flowbehavior and the stability of alditol acetals in terms of odor but alsothat this double capacity does not produce any deterioration in theeffectiveness of these products and may even increase this effectivenessquite significantly. In the case of glycerol, sorbitol, pentaerythritoland vitamin E, for example, a synergistic effect can be observed interms of the reduction of haze.

EXAMPLE Preparing a Composition of MDBS in Accordance With Example 1 ofPatent JP 9-286788

In accordance with the method described in example 1 of patent JP9-286788, 10 g of pentaerythritol are dispersed in 400 ml ofisopropanol.

A suspension of 90 g of MDBS in 600 g of methanol is added. The MDBSused is in the form of a powder which does not flow freely and has a lowaerated density (148 g/l).

The mixture is heated under reflux with stirring for 30 minutes thenevaporated to dryness under vacuum. The product obtained is thencrushed.

This product has very poor flow behavior and is tacky. The aerateddensity is not increased; rather, to the contrary, it is significantlyreduced (125 g/l).

I claim:
 1. An alditol acetal composition with improved flow behaviorand/or improved stability, including at least one alditol acetal and atleast one additive selected from the group consisting of tocopherols andtheir derivatives and polyols and their non-fatty derivatives, andhaving an aerated density greater than 250 g/l and of at most 700 g/l.2. A composition according to claim 1, wherein the alditol acetal is analditol diacetal selected from the group consisting of1,3-2,4-di(benzylidene) sorbitol (DBS), 1,3-2,4-di(benzylidene) xylitol(DBX) and their derivatives.
 3. A composition according to claim 2,wherein the derivatives are alkylated and/or halogenated derivatives. 4.A composition according to claim 2, wherein the alditol acetal isselected from the group consisting of DBS and its alkylated derivatives.5. A composition according to claim 4, wherein the alditol diacetal isselected from the group consisting of methylated derivatives of DBS. 6.A composition according to claim 5, wherein the alditol diacetal isselected from the group consisting of methylated derivatives of DBSobtained by dehydrocondensation of sorbitol and a benzaldehyde which ismethylated in at least position 3 or 4 of its ring.
 7. A compositionaccording to claim 1, comprising 50 wt. % to 99 wt. % of alditolacetal(s), and 1 wt. % to 50 wt. % of additive(s), these percentagesbeing expressed with respect to the total weight of alditol acetal(s)and additive(s) contained in said composition.
 8. A compositionaccording to claim 7, comprising 1 wt. % to 20 wt. % of additive(s). 9.A composition according to claim 8, comprising 3 wt. % to 20 wt. % ofadditive(s).
 10. A composition according to claim 1, said compositionbeing in a powdery and/or granular form.
 11. A composition according toclaim 10, said composition being in the form of densified or compactedpowder, granules, pellets, pastilles or extrudates.
 12. A compositionaccording to claim 1, having an aerated density in the range 275 g/l to700 g/l.
 13. A composition according to claim 12, having an aerateddensity in the range 300 g/l to 650 g/l.
 14. A composition according toclaim 13, having an aerated density in the range 300 g/l to 490 g/l. 15.An alditol acetal composition with improved flow behavior and/orimproved stability, containing at least one alditol acetal and at leastone additive selected from the group consisting of tocopherols and theirderivatives and polyols and their non-fatty derivatives, said alditolacetal and said additive being subjected, in the presence of each other,to a shaping and/or densification process.
 16. An alditol acetalcomposition according to claim 15, wherein the shaping and/ordensification process is granulation, compaction or extrusion.
 17. Acomposition according to claim 15, wherein the alditol acetal is analditol diacetal selected from the group consisting of1,3-2,4-di(benzylidene) sorbitol (DBS), 1,3-2,4-di(benzylidene) xylitol(DBX) and their derivatives.
 18. A composition according to claim 17,wherein the derivatives are alkylated and/or halogenated derivatives.19. A composition according to claim 17, wherein the alditol acetal isselected from the group consisting of DBS and its alkylated derivatives.20. A composition according to claim 19, wherein the alditol diacetal isselected from the group consisting of methylated derivatives of DBS. 21.A composition according to claim 20, wherein the methylated derivativesof DBS are those obtained by dehydrocondensation of sorbitol and abenzaldehyde which is methylated.
 22. A composition according to claim15, comprising 50 wt. % to 99 wt. % of alditol acetal(s), and 1 wt. % to50 wt. % of additive(s), these percentages being expressed with respectto the total weight of alditol acetal(s) and additive(s) contained insaid composition.
 23. A composition according to claim 22, comprising 1wt. % to 20 wt. % of additive(s).
 24. A composition according to claim23, comprising 3 wt. % to 20 wt. % of additive(s).
 25. A compositionaccording to claim 15, said composition being in a powdery and/orgranular form.
 26. A composition according to claim 25, said compositionbeing in the form of densified or compacted powder, granules, pellets,pastilles or extrudates.
 27. A composition according to claim 15, havingan aerated density in the range 275 g/l to 700 g/l.
 28. A compositionaccording to claim 27, having an aerated density in the range 300 g/l to650 g/l.
 29. A composition according to claim 28, having an aerateddensity in the range 300 g/l to 490 g/l.
 30. Plastics materials orjellified materials comprising a composition according to claim
 1. 31.Plastics materials or jellified materials comprising a compositionaccording to claim 15.